JP2001227320A - Active muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify an active muffler constituted complicatedly by separately arranging a muffling signal output means and a cooling fan to cool it in case of providing this conventional active muffler on an exhaust pipe of an engine. SOLUTION: A muffling signal output means 3 and a means 7 to cool the muffling signal output means 3 are arranged in the same case 44, the cooling means 7 is arranged on the back surface side of the muffling signal output means 3 to cool the muffling signal output means by sending cooling air from an outer periphery of the muffling signal output means and a plural number of the cooling means are arranged in the case on an active muffler having a first noise detection means on a duct arranged on the noise source side, a means arranged on the downstream side of the duct and to output a muffling signal, a computing means to compute the muffling signal of an antiphase against the noise signal detected by the first noise detection means and a second noise detection means arranged on the downstream side of the output means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise reduction device, in which an output means for outputting a noise reduction signal having a phase opposite to a noise signal is cooled so as not to be damaged by heat from an exhaust pipe of an engine. .

[0002]

2. Description of the Related Art Conventionally, active muffling has been provided in which a speaker is provided in a duct such as an engine exhaust pipe, an air supply duct, and a ventilation duct, and a signal having a phase opposite to that of the noise in the duct is output from the speaker. The device is known. When such an active noise reduction device is disposed in an exhaust portion such as an muffler of an engine, a means for outputting a noise reduction signal such as a speaker is disposed at an end of a branch pipe branched from a noise passage duct.

[0003]

However, since the high-temperature exhaust gas from the engine passes through the duct through which the noise passes, the high-temperature heat may enter through the branch pipe and damage the output means. Therefore, in order to prevent the output means from being destroyed by heat, a cooling fan is provided to cool the output means with cooling air.However, the cooling fan and the sound output means are arranged in separate cases, and Since the cooling air was sent by communicating between the cases with pipes or ducts, the cooling air passage became long, and the cooling air was heated while passing through the passage and the wind power dropped, resulting in poor cooling efficiency Had become. Further, when the cooling fan fails, the output means is exposed to high temperature and is damaged, so that active noise reduction cannot be performed. Therefore, the present invention simplifies the mounting configuration of the cooling fan and the silencing signal output means, so that even if the cooling fan is broken, the cooling fan is cooled by another cooling fan so that active silencing can be continued.

[0004]

The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described. That is, in the first aspect, the first noise detection means in the duct disposed on the noise source side, the means for outputting a muffling signal disposed downstream of the duct, and the first noise detection means Calculating means for calculating a muffling signal having an opposite phase to the detected noise signal, and a second muffler detecting means disposed downstream of the output means. The means and means for cooling the muffling signal output means are arranged in the same case.

According to a second aspect of the present invention, the cooling means is disposed on the back side of the muffling signal output means, and the cooling means is used as a cooling fan to send cooling air from the outer periphery of the muffling signal output means for cooling.

According to a third aspect of the present invention, a first noise detecting means is provided on a duct arranged on a noise source side, a means for outputting a muffling signal is arranged on a downstream side of the duct, and In an active noise reduction device having a calculation means for calculating a noise reduction signal having an opposite phase to the noise signal detected by the detection means, and a second noise detection means arranged downstream from the output means, A plurality of cooling means are arranged in a case accommodating the silencing signal output means.

According to a fourth aspect of the present invention, the plurality of cooling means are arranged in series, and one of them is used as a spare for the other.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration and control of the active silencer of the present invention, FIG. 2 is a cross-sectional view of a silencing signal output means mounting portion, FIG.
Is a sectional view of an embodiment provided with a plurality of cooling means, FIG. 5 is a sectional view showing another embodiment, and FIG. 6 is a side view of the embodiment.

First, an outline of an active noise reduction device will be described with reference to an example of an active noise reduction device 10 configured to mute exhaust noise of an engine generator. FIG. 1 shows a schematic configuration of the active silencer. A sound source passage duct 1 is connected to an exhaust pipe of an engine 2a of an engine generator 2 serving as a noise source (primary sound source) to form a one-dimensional sound field so that noise flows from left to right in FIG. On the noise source side of the sound source passage duct 1, that is, on the engine side (left side in FIG. 1), a first sound wave sensor 4 composed of a microphone is provided as first noise detection means. On the downstream side of the sensor 4 (on the right side in FIG. 1), a second sound sensor 6 composed of a microphone is provided as second noise detecting means.

The first sound wave sensor 4 of the sound source passage duct 1
A branch pipe 1a is arranged between the second sound wave sensor 6 and
A branch port 1b is opened in the branch pipe 1a, and a branch pipe 9 is communicated with an end of the branch port 1b. A speaker 3 as a silencing signal output means and a cooling means as a cooling means are connected to the end of the branch pipe 9 at the end. A cooling fan 7 is arranged, and a temperature sensor 13 is provided near the speaker 3.
Are arranged, and the temperature of the speaker 3 is detected. Then, the sound source passage duct 1 is cooled by the cooling fan 7.
The speaker 3 is cooled so as not to be damaged by heat transmitted from the speaker 3.

The branch pipe 1a and the first sound wave sensor 4
A passive silencer 11 composed of a plurality of sound arresters is arranged between the two, and in this embodiment, two passive shunts 11a and 11b are arranged in series to form the passive silencer 11. The passive silencer 11 silences and reduces high frequency noise. However, in the present embodiment, the passive silencer 11 is arranged upstream of the sound source passage duct 1, but may be arranged in the middle or downstream of the sound source passage duct 1.

The passive silencer 11 is formed, for example, in a substantially cylindrical shape, and has a sound absorbing member provided on an inner peripheral portion thereof. The sound absorbing member silences noise passing through the passive silencer. Have been. The internal volume of the passive silencer 11 provided with a sound absorbing member therein is set such that the effect of silencing high frequency noise is enhanced. The first acoustic wave sensor 4, the second acoustic wave sensor 6, the cooling fan 7, and the temperature sensor 13 are connected to the controller 5, and the speaker 3 is connected to the controller 5 via the amplifier 12.

The first sound wave sensor 4 detects exhaust sound which is noise, the speaker 3 outputs a sound wave having a phase opposite to that of the exhaust sound to mute the sound, and the second sound wave sensor 6 has a muffling function. Is monitored and fed back to the controller 5. The controller 5 calculates and calculates a muffling signal having a phase opposite to that of the noise signal detected by the first sound wave sensor 4, and calculates and outputs a more efficient muffling signal from the feedback signal.
0, the engine generator 2 and the alarm device 1
6 etc. are controlled.

The alarm device 16 includes a lamp 17 and a buzzer 19
The cooling fan 7 is constantly driven while the engine generator 2 is operating, and when the engine generator 2 is stopped, it is determined that the detection value of the temperature sensor 13 is equal to or higher than the first set temperature. Then, the driving of the cooling fan 7 is continued, and when the temperature becomes equal to or lower than the second set temperature, the cooling fan 7 is stopped. In addition, after the engine generator 2 is stopped by connecting the timer 18 to the controller 5, the cooling fan 7 is driven for a set time to prevent the speaker 3 from being damaged by the residual heat. Alternatively, the cooling fan 7 is stopped when the time reaches earlier. Further, when the temperature of the temperature sensor 13 becomes equal to or higher than the third set temperature, the temperature is abnormally increased. In this case, the alarm device 16 is operated to make the operator recognize and stop the engine generator 2.

The operation of the active silencer constructed as described above will be described. That is, when the engine generator 2 is operated, when the engine is operated and the exhaust gas is exhausted from the sound source passage duct 1, the accompanying exhaust sound is detected by the first sound wave sensor 4, and the detection signal is transmitted to the controller 5. When the detection signal is input, the controller 5 generates a silence signal having the same amplitude and opposite phase. This silence signal is output to the speaker 3 via the amplifier 12, and
A sound-absorbing sound wave is output. Since the noise-reducing sound wave is made to have the same amplitude in the opposite phase to the exhaust sound emitted from the sound source passage duct 1, the exhaust sound is canceled by the noise-reducing sound wave, and the sound-muffling action is performed. . Further, a synthetic sound wave of the exhaust sound and the sound wave for silencing is detected (monitored) by the second sound wave sensor 6, and the result of the silencing operation is fed back to the controller 5, and the silencing signal is corrected so that the silencing operation is performed more sufficiently. Because

In general, the exhaust noise component is a relatively low frequency component composed of a component mostly determined by the engine speed and the number of cylinders and its harmonics. Upon detection, the lower the frequency component, the greater the degree of enhancement. For this reason, the first sound wave sensor 4
If the output signal is input to the controller 5 as it is, the noise canceling effect on the low frequency components increases, but the noise canceling effect on the components in the frequency region where the sensitivity is high and the noise tends to be harsh is insufficient.

Therefore, a passive silencer 11 is further provided in the active silencer 10 to provide a passive silencer having a high silencing effect in a high frequency range in addition to the silencing effect of the active silencer having a high silencing effect in a low frequency range. 11
Thus, the silencing effect is improved in all frequency ranges.

Next, the cooling configuration of the sound output means of the present invention will be described. First, the first embodiment of the speaker unit S provided with one cooling fan 7 will be described. 1 and 2,
In FIG. 3, a branch pipe 1a is formed as a T-shaped pipe, and a branch pipe 9 is communicated with a branch port 1b. A speaker 3, a cooling fan 7, and a temperature sensor 13 are integrally formed at the other end of the branch pipe 9. Are located. That is, the speaker 3 is fixed to the tip of the branch pipe 9, a part of the end of the branch pipe 9 is overlapped, and a cooling case 44 is fixed around the outer periphery of the branch pipe 9 to house the speaker 3. Although the shape is not limited to the portion where the branch pipe 9 and the cooling case 44 overlap, for example, a space such as a donut shape is formed and used as the air chamber 39. A communication hole 9 formed in a relatively small hole in the outer peripheral portion of the branch pipe 9 where the air chamber 39 is located.
are opened, and the inside of the cooling case 44 and the inside of the branch pipe 9 are communicated.

An air introduction pipe 45 is connected to the other end of the cooling case 44, and is connected to an air source (for example, the atmosphere). The introduction pipe 45 is connected to the cooling case 44
The cooling fan 7 is provided inside the communication port 44a communicating with the cooling fan 7. That is, the cooling fan 7 is arranged on the back side of the speaker 3 (hereinafter, the side that emits sound is the output side and the front side, and the side opposite to the output side is the back side), and one cooling case is provided. The speaker 3 and the cooling fan 7 are accommodated in 44 and are compactly arranged so that assembly is easy. The cooling fan 7 is not limited to an axial fan or a cross-flow fan, but a turbo fan is used in this embodiment.

As shown in FIGS. 2 and 3, the discharge portion of the cooling fan 7 is connected to a communication hole 44b opened on the side surface of the cooling case 44. On the other hand, a communication hole 44c is opened on the side surface of the overlapping portion (air chamber 39) of the cooling case 44 in which the communication hole 9a is arranged, and the communication hole 44b and the communication hole 44 are formed.
c, a semi-cylindrical communication pipe 46 is formed on the outer surface of the cooling case 44.
Has been fixed. That is, the communication pipe 46 and the discharge port of the cooling fan 7 communicate with each other through the communication hole 44b.
The communication pipe 46 and the air chamber 39 communicate with each other via c, and the communication pipe 46 bypasses the speaker 3. The air chamber 39
And the branch pipe 9 are communicated with each other through the communication hole 9a.
Is discharged from the outer periphery of the speaker 3 to the signal output side of the speaker 3. However, the communication hole 44
The opening area of b · 44c is configured to be larger than the communication hole 9a.

In such a configuration, when the temperature sensor 13 exceeds the first set temperature, such as when the engine 2a of the generator 2b is driven or immediately after the engine 2a is stopped,
The cooling fan 7 is driven to cool the front part of the speaker 3. That is, the driving of the cooling fan 7 causes the introduction pipe 4
5, the air is sucked through the discharge port of the cooling fan 7, and the communication hole 44b, the communication pipe 46, the communication hole 44c, the air chamber 3
9. The cooling air enters the branch pipe 9 through the communication hole 9a and is sent to the sound source passage duct 1 side to cool the front part of the speaker 3.

By sending the cooling air from the cooling fan 7 to the air chamber 39 through the communication pipe 46, the air chamber 3
9 serves as a pressure accumulating chamber, and discharges into the branch pipe 9 through a plurality of small-opened communication holes 9a, 9a,... On the outer periphery of the branch pipe 9 at the front part of the speaker 3, and the front part of the speaker 3 is an air curtain. This makes it difficult for hot air to reach the speaker 3, thereby preventing the speaker 3 from being damaged by high temperature.

Next, an embodiment of a speaker unit S 'provided with a plurality of cooling fans 7 will be described. In this embodiment, the case where two cooling fans 7 are provided will be described, but three or more cooling fans 7 may be provided. As shown in FIG. 4, the cooling fans 7 are arranged in series in the same cooling case 44 in the axial direction of the cooling case 44, and the side close to the speaker 3 is a main cooling fan 7a, and the other is a spare cooling fan 7b. , Each of which is connected to the controller 5. The main cooling fan 7a and the speaker 3 are fixed to a cylindrical support case 63, and the support case 63 is fixedly supported in the cooling case 44 via a gap to form a double structure.
A check valve 71 is provided at each of the discharge port of the main cooling fan 7a and the discharge port of the preliminary cooling fan 7b, and is opened in the cooling case 44. The check valve 71 increases the pressure from the speaker 3 side. Therefore, the hot air is prevented from flowing back, or the cooling air can be sent to the speaker 3 when one of the cooling fans is driven and the other is stopped. However, the structure of the check valve 71 is not limited. And
The gap between the cooling case 44 and the support case 63 communicates with the branch pipe 9 at the front. In other words, the cooling air flows from the outer periphery of the speaker 3 to the front part of the speaker 3. The suction port of the main cooling fan 7a communicates with the connection pipe 64, and the connection pipe 64 is connected to the cooling case 44.
And is connected to the introduction pipe 45.

As described above, when the engine generator 2 is driven or immediately after the engine is stopped, when the temperature exceeds the set temperature, the main cooling fan 7a is driven, and the air is introduced through the introduction pipe 45 and the connection pipe 64. Is sucked and discharged into the cooling case 45 so that the cooling case 44 and the supporting case 6
The cooling air is discharged to the front part of the speaker 3 from the gap between the three.
The speaker 3 is prevented from being damaged by heat from the sound source passage duct 1. When the main cooling fan 7a breaks down, an alarm is issued and the preliminary cooling fan 7b is driven to suck air from the introduction pipe 45 and discharge the air into the cooling case 45 in the same manner as described above. From the gap between the cooling case 44 and the support case 63, the speaker 3
The cooling air is discharged to the front to cool the speaker 3 and prevent the speaker 3 from being damaged.

The structure of the main cooling fan 7a and the speaker 3 can be substantially the same as that of the speaker unit S. The speaker unit S "is connected to the speaker 3 and the main unit as shown in FIGS. The cooling fan 7a and the pre-cooling fan 7b are housed in the cooling case 44 in a substantially serial manner, and the main cooling fan 7a is fixed to a partition plate 44d provided at the center of the cooling case 45, and an inlet of the main cooling fan 7a. Is communicated with the introduction pipe 45 via a pipe 60. The pipe 60 extends from the suction port of the main cooling fan 7a to the outside of the cooling case 44 once so as to bypass the pre-cooling fan 7b, and is branched. And the like, and communicates with the introduction pipe 45.

The suction port of the pre-cooling fan 7b communicates with an introduction pipe 45, and the discharge port communicates with a communication hole 44e provided in the cooling case 44. The communication hole 44e is a semi-cylindrical member fixed to the outer surface of the cooling case 44. It is open in the communication pipe 61 in the shape of a circle. The other end of the communication pipe 61 is connected to the air chamber 39.
Is communicated with a communication hole 44f provided in a cooling case 44 on the outside. As described above, the communication holes 44b and 44e are provided with check valves 71 and 71, respectively. With such a configuration, when the normal engine generator 2 is operated, the main cooling fan 7a is driven in the same manner as described above, and the communication hole in front of the speaker 3 is provided through the communication pipe 46 and the air chamber 39. 9a, 9a ... discharges into the branch pipe 9 and cools it. When the main cooling fan 7a breaks down, the preliminary cooling fan 7b is driven by the controller 5, and through the communication pipe 61 and the air chamber 39, through the communication holes 9a, 9a,. It is discharged inside and cooled. In this way, even if the main cooling fan 7a fails, the cooling air is discharged before the speaker 3 by the pre-cooling fan 7b to prevent the speaker 3 from being exposed to high heat and being damaged. However, the main cooling fan 7a and the auxiliary cooling fan 7b may be reversed. When the temperature becomes abnormally high, both the main cooling fan 7a and the auxiliary cooling fan 7b can be driven.

If the temperature near the speaker 3 is higher than the first set temperature even if the engine generator 2 is stopped,
DC-A from the emergency power supply 14 via the inverter 15
If the power is not supplied from the generator 2b to a power failure or lightning strike due to the failure of the engine 2a or the generator 2b, the cooling can be performed by driving the cooling fan 7 after the C conversion.
The cooling fan 7 is driven by the power from the emergency power supply 14.

[0028]

As described above, the present invention has the following advantages. That is, as in claim 1,
First noise detection means in a duct arranged on the noise source side,
Means for outputting a muffling signal disposed downstream of the duct, calculating means for calculating a muffling signal having an opposite phase to the noise signal detected by the first noise detection means, and from the output means In the active noise reduction device having the second noise detection means also disposed on the downstream side, the noise reduction signal output means and the means for cooling the noise reduction signal output means are arranged in the same case, so that the conventional noise reduction signal The structure is simpler than the structure in which the output means and the cooling means are housed in separate cases, the structure for guiding the cooling air can be simplified, the cost can be reduced, and the cooling air passage is shortened. In this case, the decrease in wind power was small, and the temperature rise was also small, so that the cooling efficiency could be improved.

Further, the cooling means is arranged on the back side of the silencing signal output means, and the cooling means is used as a cooling fan for cooling by sending cooling air from the outer periphery of the silencing signal output means. In addition, the cooling air is sent from the outer peripheral side of the sound output means on the rear side to the front center side, so that the high-temperature air hardly reaches the cooling means side, and it is possible to prevent the sound output signal output means from being damaged by being exposed to high temperature.

Further, the first noise detecting means is provided on a duct disposed on the noise source side, the means for outputting a muffling signal is provided on the downstream side of the duct, and the first noise detecting means is disposed on the downstream side of the duct. In an active noise reduction device having a calculation means for calculating a noise reduction signal having an opposite phase to the noise signal detected by the detection means, and a second noise detection means arranged downstream from the output means, Since a plurality of cooling means are arranged in the case accommodating the silencing signal output means, by simultaneously driving a plurality of cooling means, it becomes possible to cool in a short time even when the temperature temporarily becomes high, Even if any one of the cooling means is broken, the cooling means can be cooled by another cooling means, so that the silencing signal output means can be prevented from being damaged by high temperature, and the active silencing can be continued.

Also, since the plurality of cooling means are arranged in series and one of them is used as a spare for the other, the silencing signal output means and the cooling means can be arranged compactly with a simple structure. Even if one cooling means is broken, it can be backed up by another cooling means to cool the silencing output means, the active silencing function is not impaired, and the main body can be driven until parts are replaced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration and control of an active silencer of the present invention.

FIG. 2 is a cross-sectional view of a muffling signal output means mounting portion.

FIG. 3 is a side view of the same.

FIG. 4 is a sectional view of an embodiment provided with a plurality of cooling means.

FIG. 5 is a cross-sectional view showing another embodiment.

FIG. 6 is a side view of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sound source passage duct 2 Engine generator 3 Speaker 4 First sound wave sensor 5 Controller 6 Second sound wave sensor 7 Cooling fan 7a Main cooling fan 7b Preliminary cooling fan

Claims (4)

[Claims] A first noise detecting means disposed on a duct disposed on a noise source side; a means disposed on a downstream side of the duct for outputting a muffling signal; and a first noise detecting means detecting the noise. In an active silencer having a calculating means for calculating a silencing signal of the opposite phase to the noise signal, and a second noise detecting means arranged downstream from the output means,
An active silencer wherein the silencing signal output means and the means for cooling the silencing signal output means are arranged in the same case. 2. A cooling device according to claim 1, wherein said cooling means is disposed on the back side of said silencing signal output means, and said cooling means is used as a cooling fan to send cooling air from an outer periphery of said silencing signal output means for cooling. An active silencer according to claim 1. 3. A first noise detecting means disposed on a duct disposed on the noise source side, a means disposed on a downstream side of the duct for outputting a muffling signal, and the first noise detecting means detecting the noise. In an active silencer having a calculating means for calculating a silencing signal of the opposite phase to the noise signal, and a second noise detecting means arranged downstream from the output means,
An active silencer wherein a plurality of cooling means are arranged in a case accommodating the silencing signal output means. 4. The cooling means are arranged in series,
4. The active silencer according to claim 3, wherein one is set as the other spare.